*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
html, body{
    height: 100%;
    background-image: url(../image/game_background.png);
    background-position: center;
    background-repeat: no-repeat;
}
.nav{
    height: 50px;
    background-color: rgb(0, 202, 152);
    color: white;
    line-height: 50px;
    padding-left: 20px;
}
.container{
    width: 100%;
    height: calc(100% - 50px);
     display: flex;
     align-items: center;
     justify-content: center;
}